INDONESIA'S state watchdog said Friday the execution last year of a Nigerian man for drug offenses should not have been carried out and was the result of institutional negligence.

Humphrey Jefferson was among four men executed by firing squad at Nusa Kambangan prison island last July 29. Ten others were also due to be executed at the same time but were given a reprieve at the last moment without explanation.

Ombudsman Ninik Rahayu said the execution should not have been carried out while Jefferson's request for clemency was still underway. That it occurred was negligent, discriminatory and showed "maladministration" by the Attorney General's Office, which oversees executions, she said.

Lawyer Ricky Gunawan said the Ombudsman's report "confirms our allegations that the Attorney General's Office did violate the law."

Rahayu also blamed the Central Jakarta District Court for not conveying Jefferson's second request for judicial review to the Supreme Court and recommended it should be investigated by the higher court.

The Attorney General's Office has 60 days to respond. The Ombudsman's report can be sent to parliament and President Joko "Jokowi" Widodo.

Indonesia has harsh penalties for drug crimes and traffickers can receive the death penalty. More than 150 people are on death row, mostly for drug crimes.

A total of 18 people convicted of drug-related crimes, mostly foreigners, have been executed since Jokowi took office in late 2014. In interviews with foreign media in the past year, he has said Indonesians could be open to ending capital punishment in the future but he has not announced any steps in that direction.